Hemodynamic and respiratory effects of a xylazine-acetylpromazine drug combination in horses
Muir, W.W.; Skarda, R.T.; Sheehan, W.
American Journal of Veterinary Research 40(11): 1518-1522
1979
ISSN/ISBN: 0002-9645 PMID: 43105 Document Number: 146912
Effects of the sedative-analgesic drugs xylazine, acetylpromazine and a xylazine-acetylpromazine combination upon various hemodynamic and respiratory variables were evaluated in horses. Administration i.v. of xylazine (1.1 mg/kg) caused significant (P < 0.05) reductions in heart rate, cardiac output and respiratory rate; significant (P < 0.05) increases in central venous pressure; and significant (P < 0.05) biphasic changes, increases followed by decreases, in mean arterial blood pressure. Arterial blood gas tensions (PCO2, PO2 and pH) did not change after horses were given xylazine i.v. Administration i.v. of acetylpromazine (0.09 mg/kg) caused insignificant (P < 0.05) changes in heart rate, cardiac output and mean pulmonary arterial pressure. Respiratory rate and mean central venous and aortic pressures decreased significantly (P < 0.05) after horses were given acetylpromazine i.v. Arterial PCO2, PO2 and pH did not change after i.v. injection of acetylpromazine. Administration of a xylazine (0.55 mg/kg; i.v.)-acetylpromazine (0.05 mg/kg; i.v.) drug combination caused significant (P < 0.05) decreases in heart rate, cardiac output and respiratory rate. Mean central venous and arterial blood pressures were significantly (P < 0.05) decreased at later times after drug administration. Arterial PCO2, PO2 and pH did not change significantly (P < 0.05) from base-line values. The xylazine-acetylpromazine drug combination demonstrated varied hemodynamic effects characteristic of xylazine and acetylpromazine given individually. Behavioral changes occurring after i.v. administration of the xylazine-acetylpromazine drug combination were similar to those changes observed after xylazine administration alone and was superior to changes occurring after administration of acetylpromazine.